This invention relates generally to the use of geothermal and solar energy. More particularly, the instant invention relates to the use of geothermal and/or solar energy to environmentally condition the interior of an inhabitable enclosure.
The shortage of fuels such as gas and oil has made it quite apparent that alternative energy sources for residential and industrial heating and cooling applications must be developed. The winter of 1977 has suggested that radical changes may be necessary in design concepts conventionally associated with residential structures.
In the prior art it has long been known that geothermal and/or solar energy systems can replace fossil fuels to a certain extent. Solar energy has been used in the past to generate electricity, to provide heating internally of "greenhouse" enclosures, and to selectively provide illumination inside dwellings and the like. Geothermal energy has also been successfully employed with heating and cooling systems. Usually some form of ductwork is buried underground and connected in fluid flow communication with the enclosure interior. Alternatively, the entire enclosure may be erected underground to take advantage of natural heating and cooling effects. Even when the underground temperature is insufficient for comfort within an enclosure, geothermal heat exchanger systems may save significant amounts of energy by pre-heating or pre-cooling air within the enclosure. Examples of known prior art relevant to the latter discussion may be seen in an article entitled "Underground Houses," appearing at page 84 of the Apr., 1977 edition of Popular Science magazine; and at page 62 of the Spring/Summer edition of the magazine Home Building and Remodeling.
As is well known in the art, the outside ground surface temperature tends to vary widely, while the temperature a few feet below the surface tends to be more constant. For example, the average surface temperature recorded during a five year period at Lexington Kentucky varied between a July peak of approximately 85.degree. and a January low of approximately 35.degree.. The temperature ten feet below the ground varied between a 50.degree. low in April and an approximately 65.degree. high at the end of September. Thus the temperature variation below the surface is less extreme than the surface temperature variation. It is also clear that the underground temperature variation "lags" the variation in surface temperature. For most locations this lag is approximately 3 months.
The aforementioned time lag is suggestive of a problem often associated with conventional geothermal energy systems. The peak temperatures in the underground region in which the heat exchanger may be located occur approximately 3 months after peak surface temperatures, for example, so that this time lag does provide a certain advantage when attempting to heat a structure with geothermal energy energy when outside surface temperatures are declining. However, it is apparent that if the time lag could be extended, so that peak underground temperatures would occur closer in time to minimum surface temperatures, geothermal heating systems would be improved significantly. Obviously an increased time lag would benefit geothermal cooling systems as well.
A serious problem with conventional housing is that erection costs are increasing so rapidly that more and more people are virtually priced out of the market. The significant costs in heating or cooling a typical residence through conventional techniques are also becoming prohibitive. When steps are taken to adapt conventional housing designs to reduce energy consumption the costs associated with necessary modifications are enormous. Inexpensive alternatives to the conventional one-family dwelling, such as the increasingly popular mobile home, for example, are often notoriously vulnerable to high winds, tornadoes, hail storms and the like. It is also widely recognized that conventional low cost housing approaches are usually aesthetically inferior.